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"""Simple plug-in mechanism to provide replacement for setuptools plugins"""
class Plugin( object ):
"""Base class for plugins to be loaded"""
loaded = False
def __init__( self, name, import_path, check = None, **named ):
"""Register the plug-in"""
self.name = name
self.import_path = import_path
self.check = check
self.registry.append( self )
self.__dict__.update( named )
def load( self ):
"""Attempt to load and return our entry point"""
try:
return importByName( self.import_path )
except ImportError as err:
return None
@classmethod
def match( cls, *args ):
"""Match to return the plugin which is appropriate to load"""
@classmethod
def all( cls ):
"""Iterate over all registered plugins"""
return cls.registry[:]
@classmethod
def by_name( cls, name ):
for instance in cls.all():
if instance.name == name:
return instance
return None
def importByName( fullName ):
"""Import a class by name"""
name = fullName.split(".")
moduleName = name[:-1]
className = name[-1]
module = __import__( ".".join(moduleName), {}, {}, moduleName)
return getattr( module, className )
class PlatformPlugin( Plugin ):
"""Platform-level plugin registration"""
registry = []
@classmethod
def match( cls, key ):
"""Determine what platform module to load
key -- (sys.platform,os.name) key to load
"""
for possible in key:
# prefer sys.platform, *then* os.name
for plugin in cls.registry:
if plugin.name == possible:
return plugin
raise KeyError( """No platform plugin registered for %s"""%(key,))
class FormatHandler( Plugin ):
"""Data-type storage-format handler"""
registry = []
@classmethod
def match( cls, value ):
"""Lookup appropriate handler based on value (a type)"""
key = '%s.%s'%( value.__module__, value.__name__ )
for plugin in cls.registry:
set = getattr( plugin, 'check', ())
if set and key in set:
return plugin
return None
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